This section provides background information related to the present disclosure which is not necessarily prior art.
Bi-metallic casting techniques can be used to provide components having increased stiffness, strength, wear resistance, and other functionality. Bi-metallic casting allows two different metals to be combined in one component, while maintaining the distinct advantages offered by the constituent metals and/or alloys. In various bi-metallic casting techniques, at least a portion of base material or preform of a first metal or alloy is overcast with a second metal or ahoy. Metal preforms may have an oxide layer or oxide film on theft exterior substrate surface. Oxide layers may start as simple amorphous (non-crystalline) layers, such as Al2O3 on aluminum, MgO on magnesium and Mg—Al alloys, and Cu2O on copper. In certain aspects, their structures may derive from the amorphous melt on which they nucleate and/or grow and transform into complex and different phases and structures. The oxide layers may interfere with and/or negatively affect the ability of the metal preform to metallurgically bond with another metal under bonding conditions. Further, even if an oxide layer is once removed, there remains the possibility for another oxide layer to re-form under the appropriate oxidizing conditions and parameters. Thus, there remains a need for improved methods of forming even stronger metallurgical bonds between two metals joined using bi-metallic casting techniques.